Impact Of Realistic Mean Flow On Equatorial Waves In The Pacific Ocean

Author : Ryan Mahony Holmes
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (944 download)

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Download or read book Tropical Instability Waves and Mixing in the Equatorial Pacific Ocean written by Ryan Mahony Holmes and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique dynamics of the equatorial oceans play an important role in the El Nino - Southern Oscillation (ENSO) and the ocean's meridional overturning circulation (MOC), both of which are critical processes that drive global climate variability on a range of time-scales. This dissertation makes a number of contributions to our understanding of equatorial ocean dynamics, lateral and vertical mixing at the equator, the behavior of equatorial waves and deep equatorial mixing, with implications for both ENSO and the MOC. The main contributions are: 1) Tropical instability waves (TIWs), the main drivers of lateral eddy mixing in the eastern equatorial Pacific, share a number of dynamical features with submesoscale flows in the mid-latitudes. In particular, their formation depends on the detailed frontal dynamics and sharp vertical gradients around their fringes, with implications for TIW energetics and the accurate representation of TIWs in low-resolution ocean models. 2) TIWs drive modulations in vertical mixing by altering the vertical shear of the Equatorial Undercurrent (EUC) through horizontal vortex stretching. This modulation can drive net sea surface cooling over the eastern Pacific cold tongue that may partially offset the warming driven by TIW lateral mixing. The magnitude of the net cooling depends on the mixing scheme used to parameterize vertical mixing, with implications for the role of TIWs in the mixed-layer heat budget in different ocean models. 3) Downwelling (upwelling) equatorial Kelvin waves can drive large decreases (increases) in the amplitude of the TIW field in the eastern equatorial Pacific and thus TIW-driven lateral and vertical mixing. The Kelvin waves alter the strength and structure of the background flow from which the TIWs gain energy, resulting in complex changes to the TIW energy budget. One major sink of TIW energy, the downward radiation of waves, is strongly altered with implications for deep and abyssal equatorial ocean circulation. 4) Mixing in the abyssal equatorial Pacific can exhibit a seafloor-intensified vertical structure even over smooth topography. The generation and breaking of lee waves over smooth topography at low latitudes is one possible mechanism that could contribute to this mixing. However, downward-propagating equatorial waves generated at the surface by TIWs or wind events could also supply energy for seafloor-intensified mixing through two possible mechanisms, wave trapping due to the horizontal component of Earth's rotation and inertial instability initiated by wave-driven displacement of fluid away from the equator. These results suggest that more attention should be devoted to measuring and understanding mixing over smooth topography in the abyssal equatorial oceans because of its potential role in the global overturning circulation.